Field of the Disclosure
Embodiments of the present invention relate to a display device, and more particularly, to a display device capable of improving a picture quality.
Discussion of the Related Art
Generally, a display device displays an image by the use of thin film transistor functioning as a switching element. The display device is widely used as display devices of notebook computer, tablet computer, smart phone, portable display device, and portable information device as well as display devices of television or monitor. The display device may not be a self light emitting display device, and in such cases, may include a backlight unit for emitting light, which is disposed under a display panel. That is, the display device displays an image by the use of light emitted from the backlight unit.
According to an arrangement structure of a light source, the backlight unit may be largely classified into a direct type and an edge type. In case of the edge type, a light source is arranged at one side of a light guiding plate. In case of the direct type, a light source is arranged below a display panel. The direct type has a limitation in slimness. Thus, in case of a display device which emphasizes brightness of a screen instead of a thin profile, the direct type is generally used. Meanwhile, the edge type, which enables lightness and slimness, is used for a display device which emphasizes a thin profile, for example, display devices for notebook personal computer and personal computer monitor.
In the edge type backlight unit, an optical sheet is provided on the light guiding plate. In order to stably fix the optical sheet to the display device with a small bezel, various methods are used.
FIG. 1 is a cross sectional view illustrating a related art display device.
Referring to FIG. 1, the related art display device may include a light guiding plate 1, a reflective sheet 2, an optical sheet part 3, a receiving case 4, and a guide frame 5.
The light guiding plate 1 guides light emitted from a light source, whereby the light is guided upwardly, and a rear surface of a display panel is irradiated with the light.
The reflective sheet 2 is disposed on a rear surface of the light guiding plate 1, wherein the reflective sheet 2 reflects the light, which advances to a lower side of the light guiding plate 1, to the inside of the light guiding plate 1, to thereby improve a light efficiency.
The optical sheet part 3 is provided on the light guiding plate 1, wherein the optical sheet part 3 diffuses and concentrates the light upwardly guided by the light guiding plate 1. The optical sheet part 3 has a partially extending portion so as to be stably fixed to the display device. In this case, the optical sheet part 3 is placed onto one end of the receiving case 4.
Thus, one end of the receiving case 4 supports the optical sheet part 3, and the other end of the receiving case 4 supports the reflective sheet 2. In this case, a height of the receiving case 4 is to be lower than the optical sheet part 3 so that the receiving case 4 is provided under the partially extending portion of the optical sheet part 3 so as to support the optical sheet part 3.
The guide frame 5 surrounds edges of the backlight unit, and supports the display panel.
As shown in FIG. 1, in case of the related art display device, the receiving case 4 is provided only under the partially extending portion of the optical sheet part 3 so as to support the optical sheet part 3. Thus, if some of the light which is emitted from the light source and incident on the light guiding plate 1 is reflected to a lateral surface, the light is not reflected on the receiving case 4, and is advanced toward the guide frame 5. Thus, the light reflected to the lateral surface is reflected on the receiving case 4, and is then not incident on the display panel, whereby the light is absorbed in the guide frame 5, or is lost. That is, a brightness in the area where the receiving case 4 is provided only under the partially extending portion of the optical sheet part 3 so as to support the optical sheet part 3 is relatively lower than a brightness in the area where one end of the receiving case 4 is higher than a horizontal position of the optical sheet part 3. Accordingly, in the related art display device, there is a visible luminance difference between the area of the display panel which is overlapped with the optical sheet part with the extending portion and the area of the display panel which is not overlapped with the optical sheet part with the extending portion, thereby lowering a picture quality of the display device.